Leaf Brief -- this one is for kids (and the young at heart!)

Posted by: Bittu Sahgal on

With climate change upon us the one gift from nature that has a solution for us, is being ignored and taken for granted.


Hold a leaf in your hand. You are holding an entire factory. A most efficient and specialised food factory. And millions of billions of these little, silent factories work towards supporting life on earth through the fascinating process of photosynthesis. While the roots of the plant take in water, the pores of the leaves take in (absorb) carbon dioxide. The end product is a simple sugar and oxygen. The entire process of photosynthesis takes a fraction of a second and is a continuous process - occurring throughout the day but stopping at night. For, the process of photosynthesis depends upon light energy. When light hits the leaf surface, the chlorophyll within the leaf absorbs some of the light energy. Water gets split into hydrogen and oxygen. While the hydrogen chemically combines with the carbon dioxide to produce the simple sugar (a plant food), the oxygen produced gets released as a by-product. And what a vital by-product for life forms! So you can understand how, through this rapid conversion of light energy into chemical energy leaves make this world run. And this is also the reason why, in high-altitudes and in deserts, there is such a marked absence of life forms. Because the absence of green plants results in a rarified atmosphere - an atmosphere that lacks oxygen.

Check out the leaves in your area. On a leaf surface, you will see a series of lines that are often branched. These are the veins of the leaf and constitute the distribution network that carries water and nutrients throughout the leaf, and takes away the food that is manufactured by the leaves. You will find many kinds of leaves. On a broad basis, leaves can be readily classified into either of the two groups - simple or compound. If the leaf is one piece - it is simple. If it is divided into several parts or leaflets, it is a compound leaf. Once you have placed the leaves into either of these categories, look carefully at the shape of the leaf and its arrangement on a plant. On a stem, two leaves may be opposite each other, or they may grow alternatively. A number of leaves may also originate from a point in a whorled pattern.

From a casual glance, you might think that leaves grow at random. But this is not so. Try viewing the leaves on a stem from above and you will notice that almost every leaf, in a surface of solid green, is so positioned as to get more or less an equal exposure to sunlight. Those leaves that cannot obtain enough light (for any reason) are shed.

The shedding of leaves is a perfectly normal process, affected by a combination of various factors - daylight hours and temperature changes. In many plants, leaves fall at the beginning of the dry season. We all know this as ‘deciduous'. The short period of leaf-fall is a most striking phenomenon, totally transforming the landscape. Leaf-fall is extremely vital as it helps the plant conserve moisture; leaves give off huge quantities of water through evaporation.

Just before leaves are ready to fall, you will see many trees sporting orange, red, brown or yellow leaves. This is all a result of changes in pigment. During the period, with the changing weather depriving them of vital nutrients and moisture, the leaves' chlorophyll production falls. Under normal conditions, chlorophyll sort of retards the production of other pigments. But with the decline in chlorophyll production, the other pigments begin to dominate. The colour of the leaf changes because of a layer of cells, called the abscission layer at the base of the leaf where it meets the stalk, begins to dry up. So the leaf gets cut off from the tree's circulatory system and dies after a change in colour.

Leaves and trees are able to sequester carbon from the atmosphere better than any man-made device that scientists can possibly invent. It makes sense for us not only to protect plants, but also to appreciate them, so we can teach our children to care for these life support systems. So go out into your neighbourhood today and discover a whole new world of nature! Find a tree and commune with it, lets its protection wash over you and make a silent promise to protect to join neighbourhood campaigns to protect trees in your area for as long as you live. Your life probably depends on this.